Method of induction heating continuously moving wire



R. H. DENHAM METHOD OF INDUCTION HEATING CONTINUOUSLY MOVING WIRE Jan.18, 1949;

Filed De c .IWI m A M y Inventor: Robert, H. Denham, b War/176x) y HisAttorney.

Patented Jan. 18, 1949 METHOD OF INDUCTION HEATING CONTINUOUSLY DIOVINGWIRE Robert H. Denham, Scotia, N. Y., assignor to General ElectricCompany, a corporation of New York Application December 18, 1944, SerialNo. 568,703

(Cl. 2l913) 4 Claims. 1

My invention relates to an induction heating method, more particularlyto a method of annealing wire made of an electrically conductingmaterial, such as copper or steel, and has for its object a simple,reliable and low cost induction heatin method wherein the consumption ofelectric power is reduced to a minimum.

In carrying out my invention in one form, I provide a tank in which asuitable cooling liquid is maintained at a predetermined level, togetherwith two sheaves in the tank, one totally submerged in the liquid andthe other only partly submerged, with means for passing the wire to beannealed in two loops around the sheaves which have conical surfacesthereby to bias the turns together and form a short-circuited secondary.The arrangement is such that the upper length of the secondary leadingbetween the two sheaves consists of a single length of wire. I alsoprovide transformer means for inducing heating currents in theshort-circuited secondary and run the wire over the sheaves so that thesingle length moves from the partially submerged sheave to the otherone, during which movement it is first heated and then cooled by theliquid in the tank. Thus the generation of the heat in the wire itselfreduces the electric power required to a minimum.

In a modified form of my invention which is particularly applicable towire having 2. rectangular cross section, I pass the wire in a singleloop between the two sheaves with two turns around one sheave, whichturns are arranged one above the other to provide for electric contactbetween them.

For a more complete understanding of my invention, reference should behad to the accompanying drawing, Fig. 1 of which is a sectional view ofinduction heatin apparatus for annealing wire embodying my invention;Fig. 2 is an enlarged view in section of one of the sheaves; Fig. 3 is aside elevation View with the tank in section showing a modified form ofmy invention; Fig. 4 is a sectional view along the line 4-4 of Fig. 3looking in the direction of the arrows; Fig. 5 is a wiring diagram;while Fig. 6 is a diagram showing the arrangement of the wire loops inthe device of Fig.1.

Referring to the drawing, I provide a tank I provided with an inletopening 2 for a suitable quenching fluid, such as water, and an overflowopening 3 by means of which the quenching fluid is maintained at apredetermined level indicated by the dotted line 4. Suitably mounted inthe tank for rotation about horizontal axes and electrically insulatedfrom each other are two sheaves 5 and 6, the sheave 5 being largelyabove the liquid level 4, while the sheave 6 has its uppermost portion asubstantial distance below the liquid level 4 so as to be immersed inthe liquid.

By means of reels or spools 1 and 8, the wire 9 to be annealed is passedaround the two sheaves in two loops or turns, there being twosemicircular lengths on the outer surface of each sheave, as shown inFigs. 2 and 6. As shown in Fig. 2, each sheave is provided with atapered or conical face or surface l0, constitutin the bottom wall of aperipheral groove in the sheave, on which the two semicircular turns orlengths slide laterally toward the left hand, as seen in Fig. 2, to thepoint of least diameter whereby an electrically conducting relation ismaintained between the two lengths. It will be understood that the turnH (Fig. 2) has slipped on the tapered surface to its point of leastdiameter against the flange [2, while the turn [3 has moved downwardagainst the turn II.

By reason of the tension applied to the wire, the turn I3 is heldagainst the turn 5 l with a sub-- stantial force, and likewise the turn13a is held against the turn Hat on the sheave 5 with a substantialforce, thereby to maintain good electrically conducting relationsbetween them, whereby the wire constitutes a closed circuit secondaryconductor or loop.

The wire is moved between the two reels l and B in the directionindicated by the arrow. Preferably, a suitable driving means, such as anelectric motor I4, is applied to the reel 8 thereby to Wind wire up onthe retrieving reel 8 and apply a predetermined tension to the wire soas to rotate the sheaves and pull the wire off the feed spool I which isrestrained by suitable means (not shown). From the spool l, as indicatedin Fig. 6, the wire moves over the sheave B to form the outermost turnl3, then over the sheave 5 in the outermost turn |3a to the sheave E inthe single length I 5, then around the sheave 6 in the innermost turn H,thence to the sheave 5 and around the innermost turn Ila to the spool 8.

For heating the wire, I provide transformer means consisting of an ironcore l6 provided with a primary winding I l, the core having three legsbetween a pair of which passes the upper and lower lengths of the wire,a central leg [8 of the core extending between the lengths of wire. Whenthe primary winding is energized by suitable alternating current,currents are induced in the short-circuited secondary formed by the wireas it is fed continuously over the two sheaves.

The lower length 19 consists of two conductors and therefore, because ofthe low resistance of this length, the heat enerated in it is notsuflicient to heat it to an annealing temperature. Moreover, this lengthis completely submerged in the quenching liquid in the tank and iscooled by the liquid. However, the upper single length of wire I isheated because of its higher resistance to a predetermined annealingtemperature in passing from the sheave 5 to the sheave 6, and then atits right-hand end is cooled where it is submerged in the coolingliquid.

It will be understood that the two spools 1 and 8 are axially displacedwith respect to each other so that two outgoing and incoming wires wheretheycross each other at the point are spaced apart so as to beelectrically insulated from each other. In a typical apparatus,approximately four-fifths of the voltage induced in the secondary loopappeared across the single strand or length I5.

I also provide a tubular member 2| made of electrically insulatingmaterial, such as quartz, which is mounted in an inclined ornonhorizontal position on spaced apart cross partition walls 22 and 23in the tank so as to surround the upper wire length to form a chambersurrounding the wire for a sveamatmosphere. The right-hand end of thetube 2i extends downward into the quenching liquid in the tank below itssurface so that a small quantity of water is present in this end of thetube. In cooling, the wire raises the temperature of this water in thetube 2! to a boiling temperature, whereby a steam atmosphere ismaintained around the wire for the prevention of oxidation, the upperleft-hand end of the tube 2| being constricted to restrict the escape ofsteam around the wire.

The partition walls 22 and 23 on opposite sides of the core it andprimary winding I! are each connected with fluid-tight joints to thebottom and side walls of the tank thereby to divide the tank into twoportions at its left-hand and right-hand ends respectively and form aspace between them for the core and winding. These two tank portions areconnected together through relatively large inclined tubular member 24made of electrically insulating material adjacent the bottom of the tankthrough which extends loosely the lower double wire length l9.' The tube24 further serves to prevent the engagement of this wire length with theconducting parts of the tank in the event that the tension on the wireis relieved with consequent sag of the wire. It will be noted that thetubes 2! and 24 are substantially parallel with each other and spacedapart so that the parallel lengths of wire travel along the center linesof the tubes, the diameters of the two sheaves being the same.

Another advantage of my invention is that no tension is applied to thesingle heated length I5 other than that resulting from its own weight.This is because the semicircular turn i i (Fig. 6) has a smallerdiameter than the semicircular turn Ho and, as a consequence, the turni3a feeds wire to the spool 6 slightly faster than it is taken up by theturn I! so that no tension is applied to the single length [5.

Moreover, the 'fact that the larger diameter turn 13 or Isa on the twosheaves moves somewhat faster than the smaller diameter turn produces asmall amount of relative movement and friction between the two, wherebya good electrical connection between them is assured. If desired, thesheaves may be provided with 4 drums made of good electricallyconducting material, such as copper, to form an electrical connectionbetween the two wires. However, I have found that the jamming andfrictional action between the two turns is suificient to maintain goodelectrical contact between them.

In Fig. 3, I have shown a modified form of my invention which isespecially adapted to annealing of a rectangular wire whose turns arepositioned in superimposed relation around one sheave. The incoming wire26 is fed to the sheave 27 to form a turn 23 (Fig. 4) lying on top of aturn 29. Then the wire passes in a single turn loop around the sheave 39and then passes again around the sheave 2? to form the lower almostcomplete turn 29, after which the wire goes directly to the spool 8.Except for the difierence in the construction of the surfaces of the twosheaves, the apparatus of Fig. 23 is the same as that shown in Fig. 1.As shown in Fig. 4, each sheave is provided with a rectangularperipheral groove which is much wider than the wire to provide forlateral displacement of the outgoing wire, toward the left hand as seenin Fig. 4, as it is drawn on the sheave 2'! so that the wire as drawnoff ample clearance with respect to the incoming length 26 and the upperlength between the sheaves at the points where the outgoing wire crossesthem. Also, the groove is preferably wide enough to accommodatedifferent sizes of rectangular wire. The alignmentcf the wire on thesheaves and the superimposing of the turns on the sheave El isaccomplished by the relative axial positioning of the sheaves and theguiding of the incoming wire 25 to the sheave 2?.

As explained in connection with Fig. l, the faster traveling outer turn23 sildes somewhat with respect to the inner turn 29 thereby maintaininga good electrical connection between them and preventing any substantialtension in the single lengths of wire extending between the two sheaves.Fhis is of importance in connection with the upper length which isheated. The only tension in the upper length is that required to turnthe sheave 39.

Preferably, as shown in Fig. 5, an induction regulator 3i is provided incircuit with the primary winding l! for the control of the voltagesupplied to the winding and the temperature of the upper heated lengthof wire. Current is supplied at a suitable frequency by supply mains 32,for example, a frequency of 60 cycles. Additional control of the heatingoperation is obtained by taps 33 on the primary winding.

While I have shown a particular embodiment of my invention, it will beunderstood, of course, that I do not wish to be limited thereto sincemany modifications may be made, and I therefore contemplate by theappended claims to cover any such modifications as fall within the truespirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. The method of heating electrically conducting wire which consists inpassing the wire continuously in a loop having two turns at each end inelectrically conducting engagement with each other while maintaining theends of the wire in separated electrically insulating relation with eachother thereby to form a loop having two electrically connected turns atopposite ends with a single wire length on one side of the loop and adouble wire length on the other side of the loop, and inducing in saidloop by magnetic induc tion a heating current flowing through saidsingle and double wire lengths in series with each other so that heat isgenerated mainly in said single wire length to heat the wire to apredetermined temperature.

2. The method of heating electrically conducting wire wherein areutilized two sheaves spaced a predetermined distance apart andconstructed each to maintain two turns of wire thereon in electricallyconducting relation with each other which consists in passing the wirecontinuously at least two times around both of said sheaves whilemaintaining the ends of the wire in separated electrically insulatingrelation with each other thereby to form a loop extending between saidsheaves having two electrically connected turns on each sheave with asingle wire length on one side of the loop extending between saidsheaves and a double wire length on the other side of the loop extendingbetween said sheaves, inducing in said loop by magnetic induction aheating current flowing through said single and double wire lengths inseries with each other so that heat is generated mainly in said singlewire length to heat the wire to a predetermined temperature, and passingthe Wire continuously around said sheaves by drawing the wire from onesheave while feeding the wire to the other sheave.

3. The method of heating electrically conducting wire wherein areutilized two sheaves spaced a predetermined distance apart andconstructed each to maintain two turns of wire thereon of differentdiameters in electrically conducting relation with each other whichconsists in passing the wire continuously at least two times around bothof said sheaves while maintaining the ends of the wire in separatedelectrically insulating relation with each other thereby to form a loopextending between said sheaves having two electrically connected turnsof different diameter on each sheave with a single wire length on oneside of the loop extending between said sheaves and a double wire lengthon the other side of the loop extending between said sheaves, inducingin said loop by magnetic induction a heating current flowing throughsaid single and double wire lengths in series with each other so thatheat is generated mainly in said single wire length to heat the wire toa predetermined temperature,

and passing the wire continuously around said sheaves by drawing thewire from the smaller turn on one sheave while feeding the wire to thelarger turn on the other sheave whereby substantially no tension isapplied to said heated single length of wire.

4. The method of heating electrically conducting wire wherein areutilized two sheaves spaced a predetermined distance apart andconstructed each to maintain two turns of wire thereon of differentdiameters in electrically conducting engagement with each other whichconsists in passing the wire continuously at least two times around bothof said sheaves while maintaining the ends of the wire in separatedelectrically insulating relation with each other thereby to form a loopextending between said sheaves having two electrically connected turnsof different diameter on each sheave with a single wire length on oneside of the loop extending between said sheaves and a double wire lengthon the other side of the loop extending between said sheaves, inducingin said loop by magnetic induction a heating current flowing throughsaid single and double wire lengths in series with each other so thatheat is generated mainly in said single wire length to heat the wire toa predetermined temperature, and passing the wire continuously aroundsaid sheaves by drawing the wire from the smaller turn on one sheavewhile feeding the wire to the larger turn on the other sheave wherebysubstantially no tension is applied to said heated single length of wireand a small amount of relative movement is produced between the turns oneach sheave to assure a good electrical connection between them.

ROBERT H. DENHAM.

REFERENCES CITED The following references are of record in the file ofthis patent:

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